1. Field
The present invention relates generally to electronic filters, and more specifically to devices, systems, and methods related to receiver baseband filtering.
2. Background
Filters are used extensively today in various electronic applications. A filter is an electrical network that alters the amplitude and/or phase characteristics of a signal as the frequency of the signal changes. Thus, a filter may be used in an electronic circuit to pass signals in certain frequency ranges and attenuate signals in other frequency ranges. The behavior of a filter may be described mathematically in the frequency-domain in terms of its transfer function. The transfer function describes, among other things, the ratio between the input signal amplitude and the output signal amplitude applied of the filter. The amplitude response curve describes the effect of the filter on the amplitude of the input signal at various frequencies. The steepness of the amplitude response curve is generally described in terms of the filter's quality factor and filter order.
FIG. 1 is a block diagram illustrating a conventional filtering system 100 configured to provide receiver baseband filtering. System 100 includes an antenna 102, a low-noise amplifier 104, a mixer 106, and a continuous-time baseband filter 108. As understood by a person having ordinary skill in the art, a signal received by antenna 102 may be amplified by low-noise amplifier 104 and, thereafter, low-noise amplifier 104 may output differential signal 110 corresponding to differential input of mixer 106. Differential signal 110 may then be down-converted to baseband by mixer 106, which outputs differential baseband signal 114. Differential baseband signal 114 may then be transmitted to continuous-time baseband filter 108, which is configured to filter differential baseband signal 114 before transmitting differential baseband signal 114 to an analog-to-digital converter (not shown).
As understood by a person having ordinary skill in the art, receiver baseband filtering has conventionally involved a trade-off between acceptable passband loss and adequate adjacent channel filtering. More specifically, a filter may be configured to position poles and zeros at an adequate distance away from a desired channel and, therefore, under worst case conditions (e.g., process, voltage, and temperature conditions), filtering of the desired channel is avoided. However, this may result in reduced adjacent channel filtering. Conversely, to limit passband loss, a filter may be configured to position poles and zeros beyond the passband edge to achieve acceptable passband loss but at the expense of poor adjacent channel filtering.
There is therefore a need in the art for a receiver baseband filter configured to provide adequate adjacent channel filtering while minimizing passband loss.
In accordance with common practice the various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus (e.g., device) or method. In addition, like reference numerals may be used to denote like features throughout the specification and figures.